Here are some online resources you may find useful

Mathematical Resources:

The Abacus

A history of, directions for and working online Abacus (What was used before a calculator)

Printable Rulers and Protractor
A printable worksheet of Rulers in inches and metric, as well as a Protractor

Dictionary of Units of Measurement

A Dictionary of Units of Measurement and their conversion factors

Mathematical Reference Tables

Pretty much anything you want to know about math formulas

PRIME Mathematics Encyclopedia

Encyclopedia of Mathematical words and principles

Mac Tutor History of Mathematics

A data base of important historical mathematical contributions

Mathematical Quotes

Fun, inspiring and insightful mathematical qoutes

MAA American Mathematic

National mathematical competitions

Mathematical Help:

Drexel Math Forum
Drexels online mathematical help site which provides lectures, notes and
AAA Math
From Decimals to Statistics, AAA Math will be able to help you
Cool Math
Lessons on a variety of mathematical topics, as well as games and puzzles
Algebra
Support materials for courses on Algebra ranging from Pre~Algebra to Algebra 2 as well as Geometry.
Purple Math
Algebra help including free online tutoring, lessons, worksheets and quizes.
S.O.S. Math
Help with courses ranging from high school Algebra to college Differential Equations.

Mathematical Games:

The Math League
The Math League is a national mathematical competition, find out more information here!
Sheppard Software
From Addition to Integers, Sheppards has games for it all!
Cool Math For Kids
Geometry Games
Party Designer
Design a party with Area and Perimeter
Geometry Games
A variety of games to build up your Geometry knowledge
Algebra Games
A variety of games to solidify your Algebra skills
Save The Zogs
Save the Zogs with Linear Equations
Logic Games and Puzzles
Many different Logic Games and Puzzles

Citation Generators:

Son of Citation Machine
Easy Bib